1. Field of the Invention
The present invention relates to a decoder device used for example with a digital broadcasting receiver.
2. Description of the Related Art
FIG. 3 is an illustration showing a structure outline of a conventional digital broadcasting receiver. Concerning a digital broadcasting, in the case that audio and video (AV) are output in sync, it is necessary to time them to output them with comparing PTSs (Presentation Time Stamp), which are included in audio and video PES packets, with Local PCR (Local Program Clock Reference) value.
A concrete conventional method to time them is explained below referring to FIG. 3. TS (Transport Stream), which is derived by demodulating a digital broadcasting wave, includes a packet which describes a PCR. A receiver has a software/hardware Local PCR counter to count up in every PCR cycle (27 MHz). Because some gap between the Local PCR counter value and the PCR value in the digital broadcasting wave arises, the Local PCR is synchronized by a PLL (Phase Locked Loop) adjustment section in FIG. 3 referring to the PCR value in the digital broadcasting wave.
TS packets of AV data are included in the TS, and PES (Packetize Elementary Stream) packets of AV data are derived from these TS packets. PTS, which is time information to reproduce and output an access unit (a unit of decoded reproduction output) of the PES, is written in addition in the PES packets. In the case of using this method, a software/hardware Local PCR counter synchronized with a PCR of a broadcasting wave is a necessity (refer to the Japanese laid open patent TOKKAI 2003-348485).
However, it is possible that a digital broadcasting receiver is unable to have a Local PCR counter synchronized with a PCR of a broadcasting wave because of its hardware or software restriction.